The present invention relates to an apparatus and a method for automatically mounting window glasses on the front and rear windows of the automobile body.
In a known conventional apparatus of this kind, as in Japanese Patent Laid-Open No. 36770/1983, a jig for holding the window glass is supported on a support frame so that it can be moved back and forth on the support frame. The support frame is mounted on a robot. The robot positions that support frame at a location facing the window of the automobile body being carried on the car body conveying line and, with the support frame held at this position, the jig is advanced toward the window to mount the window glass unit. In this apparatus, the robot, which is provided to the ceiling above the car body conveying line and which is movable lengthwise and width wise of the car body, has an arm consisting of vertically swingable parallel links with the above-mentioned support frame attached to the lower end thereof. The positioning of the window glass by this robot is performed as follows. Outside the conveying line, the window glass is set in the jig. Then the robot is shifted toward the conveying line and, according to signals from various detectors attached to the support frame that detect a car body position in terms of the three directions along the length, width and height thereof, the support frame is moved in parallel with these three directions so as to be positioned at a location facing the window of the car body.
The window glass mounting apparatus mentioned above, however, has a drawback. That is, since the robot is suspended above the car body conveying line, it is necessary to carry the car body on a conveyor running on the floor in order to avoid interference with the robot. This puts constraints on the design of an automobile assembly line. For example, there arises a problem that it is not possible to adopt an assembly line in which the car body is carried by a hanger conveyor enabling both the mounting of the window glass and the assembly work associated with the under body components to be performed on the same assembly line.
Even with the above window glass mounting apparatus, it is possible to use a hanger conveyor to carry the car body if it is so arranged as to have the robot provided with a robot arm which is swingable from outside the car body conveying line toward the line. In this arrangement, the robot arm is provided at the front end with the support frame. With the arm turned away from the conveying line, the window glass is set in the jig and thereafter the arm is turned back toward the conveying line to mount the window glass. This arrangement allows the robot to be positioned outside the conveying line, which in turn permits the use of the hanger conveyor for conveying the car body.
With this arrangement, however, the weight of the support frame and jig at the front end of the robot arm causes the arm to droop forwardly downwardly, making it impossible for the window glass to be mounted at the correct position on the window portion due to the support frame inclination resulting from the front-end drooping of the arm, when the support frame is positioned simply with respect to the window portion of the car body.
The object of this invention is to provide an apparatus and a method which uses a robot having a swingable arm and which correctly mounts the window glass by adjusting the inclination of the support frame.